Neutron occupancy of the 0d5/20d5/2 orbital and the N=16N=16 shell closure in 24O

One-neutron knockout from 24O leading to the first excited state in 23O has been measured for a proton target at a beam energy of 62 MeV/nucleon. The decay energy spectrum of the neutron unbound state of 23O was reconstructed from the measured four momenta of the 22O fragment and emitted neutron. A sharp peak was found at Edecay=50±3 keVEdecay=50±3 keV, corresponding to an excited state in 23O at 2.78±0.11 MeV2.78±0.11 MeV, as observed in previous measurements. The longitudinal momentum distribution for this state was consistent with d  -wave neutron knockout, providing support for a JπJπ assignment of 5/2+5/2+. The associated spectroscopic factor was deduced to be C2S(0d5/2)=4.1±0.4C2S(0d5/2)=4.1±0.4 by comparing the measured cross section (σ−1nexp=61±6 mb) with a distorted wave impulse approximation calculation. Such a large occupancy for the neutron 0d5/20d5/2 orbital is in line with the N=16N=16 shell closure in 24O.